The Piasecki PA-97 Helistat was an American experimental heavy-lift aircraft, built by Piasecki by fastening four H-34J helicopters to a framework beneath a helium-inflated blimp envelope. The sole prototype was destroyed during a test flight, killing a test pilot and injuring another four in the course of a single incident in 1986.

https://en.wikipedia.org/wiki/Piasecki_PA-97_Helistat

NSFW Video - https://www.youtube.com/watch?v=4KY3A2HlbzQ - it's barely off the ground when it crashes at ~1:00.

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[–] DogThatWentGorp@hexbear.net 21 points 1 month ago (1 children)

That last paragraph too oh my god

the main brunt of the load that caused the structural failure was ground resonance, which effects ALL helicopters

Yeah which makes it even more crazy that whoever built this monstrosity was allowed to do it. Anything that falls apart like that as soon as it's lifted has to involve skipping so much math to check forces there's just no way.

[–] InevitableSwing@hexbear.net 20 points 1 month ago

I noticed that too. His "defense" and the crash itself reminds me of Richard Feynman's explanation about how cold weather impacted O-rings and caused the Challenger disaster. The crash coincidently also happened the same year.

NASA officials said that the chance of failure of the shuttle was about 1 in 100,000; Feynman found that this number was actually closer to 1 in 100. He also learned that rubber used to seal the solid rocket booster joints using O-rings, failed to expand when the temperature was at or below 32 degrees F (0 degrees C). The temperature at the time of the Challenger liftoff was 32 degrees F.

Feynman now believed that he had the solution, but to test it, he dropped a piece of the O-ring material, squeezed with a C-clamp to simulate the actual conditions of the shuttle, into a glass of ice water. Ice, of course, is 32 degrees F. At this point one needs to understand exactly what role the O-rings play in the solid rocket booster (SRB) joints. When the material in the SRB start to heat up, it expands and pushes against the sides of the SRB.

If there is an opening in a joint in the SRB, the gas tries to escape through that opening (think of it like water in a tea kettle escaping through the spout.) This leak in the Challenger’s SRB was easily visible as a small flicker in a launch photo. This flicker turned into a flame and began heating the fuel tank, which then ruptured. When this happened, the fuel tank released liquid hydrogen into the atmosphere where it exploded.

As Feynman explained, because the O-rings cannot expand in 32 degree weather, the gas finds gaps in the joints, which led to the explosion of the booster and then the shuttle itself.

https://feynman.com/science/the-challenger-disaster/

I don't see how four helicopters powering a blimp is in any way, shape, or form a sane idea.

Rant. The Wikipedia page for the disaster is shit because it's missing that.